Chapter 16: The Chemistry of Benzene and Its Derivatives

aryl group

substituted benzene ring

draw chlorobenzene

draw nitrobenzene

draw ethylbenzene

draw toluene

draw styrene

draw phenol

draw anisole

draw aniline

IUPAC name for ortho (o)

1,2-

IUPAC name for meta (m)

1,3-

IUPAC name for para (p)

1,4-

Which carbon is the principal functional group assumed to be at on a ring?

carbon-1

When are the o, m, p designations not appropriate?

when there are more than 2 substituents

benzene IR signal

1500 - 1600 cm^-1 and overtone pattern around 1660 - 2000 cm^-1

benzene ¹H NMR absorption

6.5 - 8 ppm

The existence of ring current is evidence of…

aromatic character

ortho coupling constant

J_ortho = 6 - 10 Hz

meta coupling constant

J_meta = 1 - 3 Hz

para coupling constant

J_para = 0 - 1 Hz

A pair of “leaning doublets” with a large ortho coupling is characteristic of…

para substitution

Benzylic protons experience a (upfield/downfield) shift relative to ordinary alkyl absorptions.

downfield

The —OH absorption in phenols is typically (higher/lower) than alcohols.

higher (5 - 6 ppm)
alc is 2 - 3 ppm

¹³C NMR absorption of benzene

100 - 160 ppm

What are the two bands that aromatic hydrocarbons have in the UV-vis spectrum?

210 nm and 260 nm

What are some important electrophilic aromatic substitution (EAS) reactions?

• halogenation

• nitration

• sulfonation

• Friedel-Crafts alkylation

• Friedel-Crafts acylation

What are the three mechanistic steps of EAS?

1. generate an electrophile

2. nucleophilic and electrophilic bond formation (hello carbocation)

3. deprotonation to regain aromaticity (bye bye carbocation)

What is the reagent for halogenation of a benzene for Br?

Br₂, FeBr₃

draw the mechanism for halogenation of benzene (Br)

draw the mechanism for nitrogenation of benzene

What is the reagent for nitrogenation of benzene?

H₂SO₄

What is the reagent for sulfonation of benzene?

H₂SO₄, SO₃

draw the mechanism for sulfonation of benzene

draw the mechanism for FC alkylation of benzene

use a large excess of benzene

How do you prevent overalkylation in FC alkylations?

use large excess of benzene